The aim of the study is: a) to determine the mechanism of insulin resistance in obese subjects. NMR studies in six healthy women showed an improvement of muscle glycogen synthesis due to a defect in glucose transport/phosphorylation which was partly reversed with weight loss; b) to evaluate differential insulin resistance in African-American and Caucasian obese women. This protocol has been completed. Results will be published in "Diabetes" this March 1998.